About building web on linux server

I have never set up a server before, but now I have built a Linux server. jdk1.7 mysql tomcat is all ready. The web published during testing is OK. If I want to develop WeChat, port 80 is required.
Question 1, first of all, I understand that port 80 is to modify tomcat port 80 (if I am wrong, please criticize me)
Question 2, after I changed port 80 and then published it to my server, I got a 502 error .

Please give me your advice. Thank you for being here~~~

Reply content:

I have never set up a server before, but now I have built a Linux server. jdk1.7 mysql tomcat is all ready. The web published during testing is OK. If I want to develop WeChat, port 80 is required.
Question 1, first of all, I understand that port 80 is to modify tomcat port 80 (if I am wrong, please criticize me)
Question 2, after I changed port 80 and then published it to my server, I got a 502 error .

Please give me your advice. Thank you for being here~~~

1 Port 80 should refer to http, 443 should refer to https

The front end uses nginx to listen to port 80, and then forwards dynamic requests to tomcat. Generally, there is no need to directly monitor port 80 with tomcat.